Thermal transformer cut-out



A. GJSTEINMAYER ET AL 2,123,260

THERMAL TRANSFORMER CUT-OUT July. 12, 1938.

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July 12, 1938. A, e. STEINMAYER ET AL 2,123,260

THERMAL TRANSFORMER CUT'OUT 2 Sheets-Sheet 2 Filed May 14, 1936 Patented July 12, 1938 UNITED STATES PATENT OFFICE 2,123,260 THERMAL TRANSFORMER CUT-OUT Alwin G. Steinmayer, Milwaukee, and Robert L. Smythe, West Milwaukee, Wis., assignors to Line Material Company, South Milwaukee, Wis., a corporation of Delaware Application May 14, 1936, Serial No. 79,686 15 Claims. (Cl. 200-124) This invention relates to thermal transformer intermediate the ends thereof. The opposite side uto t or front of the base I is provided with a pair of It is an object of this invention to provide for spaced, vertically extending parallel ribs 4, each the secondary circuit of a transformer, a therof which is provided at the lower end with a mally controlled cutout which will automatically bearing aperture 5 having a shaft 6 mounted open the circuit under a continued overload of therein. predetermined v l e, Upon the shaft 6 is mounted a switch-operat- More specifically, it is an object of this invening arm I. This arm comprises a fiat strip of tion to provide a cutout switch biased to openmetal having at the lower end a pair of spaced circuit position and having a thermally controlled ears 8 pivotally supporting the arm 1 on the shaft latch normally holding the switch in circuit-clos- 6. Cotter pins 9 extending through the shaft 6 ing position, the latch being releasable under an Serve to retain the arm 1 against lateral moveoverload of predetermined value and continued ment. for a given period of time, thereby permitting the As clearly shown in Figs. 2 and 3 and as may be switch to open automatically. observed in Fig. l, the arm 7 is provided at its A further object is to provide for the cutout upper or movable end with a U-shaped member switch a latch engaging a latching wheel normalcomprising a resilient latching finger l0 and a 1y subjected to rotative forces and held against resilient latch-retaining or guiding finger I l. rotation by a low-melting alloy which is sub- The latching finger H3 is provided with a lug enjected to heat generated by an overload in the gaging the teeth on the ratchet or latching wheel secondary circuit of a transformer, whereby soft- The ui ng fi e ll a s the pp s ening of the alloy will permit rotation of the latchside of the wheel l2 and holds the latching finger ing Wheel for releasing of the latch and automatic It! in engagement with the wheel. opening of the switch. The ratchet wheel I2 is provided with a stub Astill further object is to provide a transformer shaft I 3 imbedded in a heat-absorbing block [4 cutout unit which, if subjected to overload condipreferably composed of metal having a high melttions, will automatically open either side or both ing point and pro d d W t a Shaft-r ce n sides of a secondary circuit and which may be reap r ur c n in n a q n y of l w-m l i closed Without the necessity of renewal or replacealloy metal. The low-melting alloy metal, when ment of parts. solidified, will hold the shaft l3 against rotation It is also an object of this invention to provide and when soft, will permit rotation thereof. a transformer cutout which is more eificient in The block I4 is mounted upon a pair of spaced 7 operation, more economical to manufacture and conducting strips I5 and is secured to the base I install, and more facile in operation than proby means of bolts 20. The strips l5 are secured tective devices heretofore provided. to the base I by means of the bolts l6 extending In the drawings: through the base and by means of the nuts I7. Fig. 1 is a view in front elevation of a cutout The bolts 16 serve as terminal posts to which wire embodying this invention. terminals l8 are secured by means of the nuts l9. Fig. 2 is a sectional view in side elevati The rmj-fl has secured thereon intermediate its on the line 2-2 of Fig. l. ends, a idge 2| which extends laterally of the Fig. 3 is an upper end view of the device hown arm and beyond the ribs 4 on the base I. Each in Fig. 1. end of the bridge 2| carries a block of insulating Fig. 4 is a view in side elevation of the device material 22 which is secured to the bridge by shown in Fig. 1. means of a rivet 23' and against rotative move- Fig. 5 is a diagrammatic view illustrating the ment on the rivet by means of the slot 24 which cutout in the secondary circuit of a transformer. receives the bridge.

Like parts ares-identified by the same reference Mounted on each block 22 is a metal circuitcharacters throughout the several Views. closing plate 25 which is secured to the block by All live parts of the cutout herein disclosed are means of bolts 26. Thus the circuit-closing plate mounted upon a base I which is composed of 25 is insulated from and carried by the bridge suitable insulating material, such as porcelain. 2|. The circuit-closing plates 25 serve as cir- This base is provided upon one side at the rear cuit-closing switch members connecting the rewith a pair of spaced parallel ribs 2 extending silient brush contacts 21., The brush contacts vertically across the base, and with a rib 3;extend are mounted upon terminal blocks 28 and secured ing across the base transversely of the ribs 2 and thereto by means of bolts 29. Each terminal taken is a line terminal 32 secured to the stud by means of a nut 33.

From the foregoing, it will be observed that the circuit-closing plates 25 will be maintained in contact with the brush contacts 2'? through the bridge 2|, arm 1, latch l0 and ratchet wheel l2 which is held against rotation in the block l4.

As is illustrated in Fig. 5, corresponding ends of the conducting plates or strips it: are connected to the neutral line of the secondary and that the other corresponding ends of the conducting strips 15 are each connected to a secondary winding of the transformer. Obviously to secure interruption of the secondary circuits under given conditions, the conducting plates l5 should be composed of metal having a known characteristic resistance to a current flowing therethrough, thereby generating a predetermined quantity of heat over a given period of time.

It will also be seen, from Fig. 3, that each circuit-closing plate 25, by reason of its contact with a pair of brush contacts Zl, closes a circuit through one of the secondary windings. Thus a circuit will be established passing through each of the conducting plates l5 and, when an overload occurs in that circuit, the corresponding conducting plate [5 will be heated and its heat will be transferred to the block M.

In order to secure a definite time lag in the heating efiect of the plates l5 upon the block M,

the latter should have a predetermined cubical content requiring a given flow of current for a given period of time to raise its temperature to the melting point ofthe alloy therein. In this Way, the cutout will open under a given overload which has continued in either or both of the secondary windings during a predetermined period.

If a predetermined overload occurs for a given period of time, the temperature of the block will ultimately reach a point where the low-melting alloy metal in the block it will be softened to such extent, that the brush contacts 2'l will force the arm I about its pivot and cause the ratchet wheel l2 to rotate until the latch- I8 is released from the ratchet wheel. After the arm I is thus freed for rotation on its bearing, the circuit-closing plates 25 will be moved from the brush contacts 27 and thereby open the circuits through the secondary of the transformer.

The curved arrow 36, shown in Fig. 2, indicates the direction of movement of the arm "I as it Swings about the shaft 6 when the circuits are being opened. Preferably, the cutout should be mounted as illustrated in Figs. 1,2 and 4, thereby utilizing the force of gravity to swing the circuit-closing plates 25 completely out of contact with the brush contacts 21.

As will be clearly seen in Figs. 1 to 3, inclusive, the'arm I is provided with a stop bolt 3d having a locknut 35 for securing the bolt against rotation. The bolt 34 serves as a means for limiting the circuit-closing movement of the arm '5. The limit of this movement is determined by the engagement of the bolt 34 with the block I i.

The cutout herein disclosed is adapted to open a secondary circuit after carying an overload for a relatively long period of time and is not intended to open such circuit under short circuit conditions, this being the function of fuses. However, we are-aware of the fact that this invention may be adapted for opening a circuit under short circuit conditions and therefore, it is not to be understood that the claims are to be limited to the specific use of the device as herein disclosed.

From the foregoing, it will be apparent that We have disclosed for cutout switches a novel thermally controlled latch adapted to hold the switch in circuit-closing position during normal current demands and to release the switch for movement to open-circuit position after a predetermined overload in an electrical circuit has continued during a given period of time. It will also be apparent that the embodiment of the invention herein disclosed provides a novel cutout in which the efiicienty of the device is not affected during circuit-opening operations or by overload conditions and in which no replacement of parts is required after a circuit has been opened,

Obviously, this invention provides a cutout which may be manufactured at a relatively low cost, which will operate at comparatively no expense, and which may be serviced in a minimum period of time and with only such skill as may be necessary to reclose the switch after the lowmelting alloy metal in the block M has solidified.

We claim:

1. A cutout comprising an insulating base, a pair of terminals mounted on said base and each including a resilient contact brush in insulated relation to and inclined toward the other brush, a movable circuit-closing plate engaging said brushes to close-a circuit therethrough, an insulating block on said plate, an arm pivotally carried by said base and connected to said block in insulated relation to said plate, a latch connected to said arm, a rotatable catch engaged by said latch, a low-melting material supported by the base and normally holding the catch against rotation, and electric heating means for softening said material.

2. A cutout comprising an insulating base, a pair of terminals mounted on said base and each including a resilient contact brush in insulatedrelation to and inclined toward the other brush, a movable circuit-closing plate engaging said brushes to close a circuit there'through, an insulating block on said plate, an arm pivotally carried by said base and connected to said block in insulated relation to said plate, a latch connected to said arm, a rotatable catch engaged by said latch, a low-meltingmaterial supported by the base and normally holding the catch against rotation, and electric heating means for softening said material, said arm extending in a vertical direction about its pivotal connection with said base when held in circuit-closing position.

3. A cutout comprising an insulating base, a pair of terminals mounted on said base and each including a resilient contact brush in insulated relation to and inclined toward the other brush, a movable circuit-closing plate engaging said brushes to close a circuit ,therethrough, an insulating block on said plate, an arm pivotally carried by said base and connected to said block in insulated relation to said plate, a latch connected to said arm, a rotatable catch engaged by said latch, a low-melting material supported by the base and normally holding the catch against rotation, and electric heating means for softening said material, said arm extending in a vertical direction about its pivotal connection with said base when held in circuit closing position and being biased to move to open-circuit position upon rotation of said catch.

4. A cutout comprising an insulating base, a pair o'f-terminals mounted'on said base andeach including a resilient contact brush in insulated relation to and inclined toward the other brush, a movable circuit-closing plate 'engaging said brushes to close a circuit therethrough, an insulating block on said plate, an arm pivotally carried by said base and connected to said block in insulated relation to said plate, a latch connected to said arm, a rotatable catch engaged by said latch, a low-melting material supported by the base and normally holding the catch against rotation, and electric heating means for softening said material, said arm extending in a vertical direction about its pivotal connection with said base when held in circuit-closing position, said brushes biasing said arm toward open-circuit position.

5. A cutout comprising an insulating base, a pair of terminals mounted on said base and each including a resilient contact brush inclined toward the other brush, a movable contact plate pivotally supported by said base and insulated from said terminals when in open-circuit position, a latch secured to and insulated from said plate, a rotatable catch engaged by said latch,-

a low-melting alloy supported on said base and normally holding said catch against rotation, and electric heating means subjecting said alloy to heat generated by said means.

6. A cutout comprising an insulating base, a pair of terminals mounted on said base and each including a resilient contact brush inclined toward the other brush, a movable contact plate pivotally supported by said base and insulated from said terminals when in open-circuit position, a latch secured to and insulated from said plate, a rotatable catch engaged by said latch, a low-melting alloy supported on said base and normally holding said catch against rotation, and electric heating means subjecting said alloy to heat generated by said means, said plate extending in a vertical direction about its pivotal connection with said base when held in circuit-closing position.

7. A cutout comprising an insulating base, a pair of terminals mounted on said base and each including a resilient contact brush inclinedtoward the other brush, a movable contact plate pivotally supported by said base and insulated from said terminals when in open-circuit position, a latch secured to and insulated from said plate, a rotatable catch engaged by said latch, a low-melting alloy supported on said base and normally holding said catch against rotation, and electric heating means subjecting said alloy to heat generated by said means, said plate being biased to move to open-circuit position upon rotation of said catch.

8. A cutout comprising an insulating base, a pair of terminals mounted on said base and each including a resilient contact brush inclined toward the other brush, a movable contact plate pivotally supported by said base and insulated from said terminals when in open-circuit position, a latch secured to and insulated from said plate, a rotatable catch engaged by said latch, a low-melting alloy supported on said base and normally holding said catch against rotation, and electric heating means subjecting said alloy to heat generated by said means, said brushes biasing said plate toward open-circuit position.

9. An automatic cutout comprising an insulating base, a pair of spaced terminals, a movable contact-supporting member having a contact inand supported by said including a resilient contact brush inclined toward the other brush, a movable contact plate pivotally supported by said base and insulated from said terminals when in open-circuit position, a latch secured to and insulated from said plate, a rotatable catch engaged by said latch, a low-melting alloy supported on said base and normally holding said catch against rotation, and electric heating means subjecting said alloy to heat generated by said means, said latch comprising a latching finger engageable with one side of said catch and a guiding finger engageable with said catch.

the other side of 11. A cutout comprising an insulating base, a pair of terminals mounted on said base and each including a resilient contact brush in insulated relation to and inclined toward the other brush, a movable circuit-closing plate engaging said brushes to close a circuit therethrough, an insulating block on said plate, an arm pivotally carried by said base and connected to said block in insulated relation to said plate, a latch connected to said arm, a rotatable catch engaged by said latch, a low-melting material supported by the base and normally holding the catch against rotation, and electric heating means for softening said material, said arm extending in a vertical direction about its pivotal connection with said base when held in circuit-closing position, said latch comprising a latching finger engageable with one side of said catch and a guiding finger engageable with the other side of said catch.

12. An automatic cutout comprising an insulating base having a pair of relatively spaced substantially parallel ribs and lateral base portions extending from the ribs, a pair of spaced resilient brush contacts on each of said base portions, a pair of contact plates each connecting one of said pair of brush contacts, an insulating block secured to each of said plates, a bridge member connected to each block in insulated relation to said plates and spanning the space between said ribs, an arm secured intermediate its ends to an intermediate portion of said bridge member and pivotally mounted at one end on said ribs in insulated relation to said brushes, a latch on the free end of said arm and comprising a latching finger and a guiding finger spaced therefrom, a heat-absorbing block between said ribs base, a rotatable catch having a hub portion embedded in said block, said block including a low-melting alloy normally holding said catch and hub against rotation, said catch being disposed between and engaged by said fingers, and means for electrically heating said block.

13. An automatic cutout comprising an insulating base having a pair of relatively spaced substantially parallel ribs and lateral base portions extending from the ribs, a pair of spaced resilient brush contacts on each of said base portions, a pair of contact plates each connecting one of said pair of brush contacts, an insulating block secured to each of said plates, a bridge member connected to each block in insulated relation to said plates and spanning the space between said ribs,,an arm secured intermediate its ends to an intermediate portion of said bridge member and pivotally mounted at one end on said ribs in insulated relation to said brushes, a latch on the free end of said arm and comprising a latching finger and a guiding finger spaced therefrom, a-heat-absorbing block between said ribs and supported by said base, a rotatable catch having a hub in said block, said block including a low-melting alloy normally holding said catch and hub against rotation, said catch being disposed between and engaged by said fingers, means for electrically heating said block, and an adjustable stop on said arm engageable with said block.

14. An automatic cutout comprising an insulating base having a pair of relatively spaced substantially parallel ribs and lateral base portions extending from the ribs, a pair of spaced resilient brush contacts on each of said base portions, a pair of contact plates each connecting one of said pair of brush contacts, an insulating block secured to each of said plates, a bridge member connected to each block in insulated relation to said platesand spanning the space between said portion embedded ribs, a latch connected to said bridge and comprising a latch finger and a guiding finger, said bridge being movably supported by said base in insulated relation to said brushes and being biased to open-circuit position by said brushes, a heat-absorbing block supported by said base, a rotatable catch havinga hub portion embedded in said block, said block including a low-melting alloy normally holding said catch against rotation, said catch being engaged by and between said fingers, and means for electrically heating said block.

15; An automatic cutout comprising an insulating base, a switch-operating arm pivotally carried by said base, engageable contact means carried by said base and said arm, said members being in insulated relation to said arm and in-, 

